The bottom bracket chainrings were disassembled to solve the clunking and chain jumping issues. While apart, I clearanced out the crank arm, the part that spins over the four mounting bolts. The new 72t'ssprocket's bolt holes were beveled out to provide even more clearance. The old pocket bike freewheel was still good, so I squeezed some grease into its cracks. New locknuts were installed; the last thing I needed was the chainrings falling apart.
Sure enough, when I flipped over the dished 30t bicycle sprocket at the chainring, the bike chain lined up like it did before I swapped sprockets.
When all the pieces were together, all chains and sprockets pedalled smoother than ever before.
The test ride to and from the auto parts store went well, except the chain was skipping gears at the cassette. This had started happening a few days before I swapped the sprockets. Nothing that minor derailleur adjustment can't fix.
I can't wait for the sun to rise, so I can ride my bike to work.